Device for electroinically connecting and disconnecting portions of an electrical line, public address system, method for detecting a failure in an electrical line

ABSTRACT

The present disclosure includes devices, systems, and methods for electrically connecting and disconnecting portions of an electrical line of a public address system. One device includes a switch configured to electrically connect and disconnect a first and a second contact point, wherein the first and the second contact point are configured to be electrically connected to respective portions of the electrical line, a controller configured to control the switch based on at least one electrical characteristic at the first and/or second contact point, and a power supply configured to be electrically connected to the first contact point via the switch.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16/226,236, filed Dec. 19, 2018, which published as U.S. Publication No.2019-0200129 A1 on Jun. 27, 2019 and will issue as U.S. Pat. No.11,425,501 on Aug. 23, 2022, which claims priority to EP Application No.17208620.9 filed Dec. 19, 2017, which is incorporated herein byreference in its entirety.

The invention relates to a device for electrically connecting anddisconnecting portions of an electrical line of a public address system,a public address system and a method for detecting a failure in anelectrical line of a public address system.

STATE OF THE ART

Public address systems in public areas, which are used for danger orhazard alarms, underlie high safety and quality standards. Morespecifically, public address systems comprising loudspeakers connectedvia a line to an control and audio output module which is configured tooutput a preferably constant pilot tone and an audio signal to the linehave to be configured such that a short-circuit and/or a line breakagedoes/do not lead necessarily to a failure of the whole public addresssystem.

It is known from the EP 2 584 792 A1 to implement a loudspeaker lineexamination system for the above public address systems by applying apilot signal, which is combined with the audio signal and supplied tothe loudspeaker line from control and audio output module. Outputsignals of a current detecting circuit and a voltage detecting circuitdisposed in the control and audio output module are analysed and animpedance at the frequency of the pilot signal is computed to detect aline breakage or a decrease in impedance of the loudspeaker line.

EP 2 203 912 B1 discloses a connecting/disconnecting device for anelectrical line of a public address system. The connecting/disconnectingdevices includes a monitoring unit for checking electric characteristicsof portion of the electrical line, an energy storage device coupled tothe monitoring unit such that the function of the monitoring unit can bemaintained in case of a failure of electrical line, and a switchingelement, which is coupled to the monitoring unit and which is equippedsuch that in case of a failure of the electrical line the electricalline can be separated.

In case of a short circuit during the operation of the above publicaddress system all the connecting/disconnecting devices will detect afailure, i.e. a fault, and disconnect all portions of the electricalline. Since the control and audio output module continues to supply thepilot tone to the first portion of the electrical line, the firstconnecting/disconnecting device will detect the presence of the pilotsignal and close again the switching means. Subsequently the nextconnecting/disconnecting device along the loop will receive the pilotsignal and close its switching means. This process will continue untilreaching the connecting/disconnecting device adjacent to the failure.This connecting/disconnecting device will close the switching means,detect the fault and immediately will open the switching means again.This connecting/disconnecting device will such memorize that it islocated immediately adjacent to the fault.

Due to the switching into the fault the other connecting/disconnectingdevices located along the loop between the control and audio outputmodule and the connecting/disconnecting device adjacent to the faultwill open their switching means again, and the sequential closingprocedure will have to start again. However, this time theconnecting/disconnecting means located immediately adjacent to the faultwill not close its switching means.

Subsequently, the pilot signal is applied from the other side of theloop to the electrical line by the control and audio output module, aswell, and the sequence of closing the switching means and connectingrespective portions of the electrical line will be performed for theremaining part of the electrical line. At the end, allconnecting/disconnecting devices will have their switching means closed,apart of the two connecting/disconnecting devices immediately adjacentto the fault.

Nevertheless, with an increasing number of connecting/disconnectingdevices connected to the electric line of the public address system ittakes a long time to sequentially connect the respective portions of theelectrical line. During this time the operation of the public addresssystem is impaired.

OBJECT(S) OF THE INVENTION

In the light of the above, it is an object of the present invention toprovide a device for electrically connecting and disconnecting portionsof an electrical line of a public address system, a public addresssystem, and a method for detecting a failure in an electric line of apublic address system being able to reduce the time for re-establishingthe operation of the public address system after a detection of a fault.

The above described object is solved with a device according to claim 1,a system according to claim 9, and a method according to claim 11. Thedependent claims are directed to different advantageous aspects of theinvention.

Solutions

According to the invention there is provided a connecting/disconnectingdevice for electrically connecting and disconnecting portions of anelectrical line of a public address system. The device comprises aswitching means (e.g., a switch) which is configured to electricallyconnect and disconnect a first and a second contact point, wherein thefirst and the second contact points are configured to be electricallyconnected to respective portions of the electrical line, a control means(e.g., a controller) which is configured to control the switching meansbased on at least one electrical characteristic at the first and/orsecond contact point, a power supply means (e.g., a power supply)configured to be electrically connected to the first contact point viathe switching means, wherein the switching means is configured to switchbetween (a) a first configuration where the first contact point and thepower supply means are electrically connected with each other while thefirst and the second contact points are electrically disconnected fromeach other, and (b) a second configuration where the first contact pointand the power supply means are electrically disconnected while the firstand the second contact points are electrically connected with eachother.

Since in the first configuration the local power supply means isconnected with at least one of the contact points and with thecorresponding portion of the electrical line so as to apply electricalpower to the portion of the line between its ownconnecting/disconnecting device and the next connecting/disconnectingdevice along the electrical line, and since the control means monitorsan electrical characteristic of this portion of the line, it is possibleto determine the presence or absence of a fault—like a short circuit ora line breakage—in this portion of the electrical line adjacent to theconnecting/disconnecting device. Since this determining can be donesimultaneously by all the connecting/disconnecting devices arrangedalong the loop of the public address system, the portion of the linewith the fault can be identified almost immediately and the otherconnecting/disconnecting devices, not immediately adjacent to the faultportion, can switch into the second configuration so as to re-establishthe operation of the line.

Preferably the connecting/disconnecting device further comprises atransforming and rectifying means which is electrically connected to atleast one of the first and the second contact points and is configuredto transform alternating current supplied via the electrical line intodirect current, and a charging means for charging a power sourceconnected to the power supply means with the direct current.

Since the power supply means is connected with a power source, which inturn is charged through the electrical line during normaloperation—preferably using the power provided by a pilot signal with afrequency outside the audible range—the connecting/disconnecting deviceof the invention can operate in a reliable and effective manner for along time without the need of exchanging a battery.

Furthermore, in a preferred embodiment the control means is furtherconfigured to control the switching means such that the switching meansswitches from the second to the first configuration when a voltage atthe first contact point is lower than a predetermined threshold valueand/or a voltage at the second contact point is lower than thepredetermined threshold value.

To use the voltage as electrical characteristic to be monitored allows asimple and economic design of the connecting/disconnecting device.

It is further preferred, that the switching means comprises a firstswitch and a second switch electrically connected to each other inseries between the first contact point and the second contact point.

By providing two switches and preferably by connecting the power supplymeans at a point between the two switches in the first configuration, itis possible to apply the electrical power from the power supply meanseither in a clockwise direction of the loop, e.g. by closing the righthand switch only, or in a counter clockwise direction by closing theleft hand switch only. Preferably, the connecting/disconnecting devicesalong the loop are configured to simultaneously adopt the firstconfiguration with the left hand switches closed and subsequently amodified first configuration with the right hand switches closed. As aresult, each connecting/disconnecting device will have checked whetherthe two portions of the electrical line, which are connected to the twocontact points, are free from faults or not.

In a further advantageous embodiment the control means is furtherconfigured to store timing information concerning the at least oneelectrical characteristic at the first and/or the second contact points.

These historical data can be very helpful in further analysing the faultdevelopments of the electrical line, e.g. in case of a creeping short orline breakage.

It is additionally preferred, that the power supply means is configuredto apply at least one DC pulse, preferably a DC pulse pattern, to theelectrical line, and the control means is configured to control theswitching from the first to the second configuration depending on thedetection of the DC pulse or the DC pulse pattern received via theelectrical line, in order to detect the absence of a short-circuitand/or a line breakage.

When using a capacitor as a power source connected via the power supplymeans it is easy to provide a DC pulse to a contact point and to theline, and it is equally easy to detect such a DC pulse arriving at theother contact point through the line. If on the other hand no DC pulseis received within a predetermined waiting period, theconnecting/disconnecting device determines that the portion of the lineconnected to the monitored contact point is defect.

In a preferred embodiment, the connecting/disconnecting device comprisesa resetting means for setting the connecting/disconnecting device into adefault mode, an orientation determining means for determining in thedefault mode at which contact point a pilot tone or a switchinginstruction from a control and audio output module of the system isdetected first, and a configuration setting means for setting thecontact point receiving the pilot tone or the switching signal first asa first contact point and the other contact point as a second contactpoint.

The connecting/disconnecting device in the preferred embodiment willsynchronously monitor the portions of the electrical line in a clockwisedirection and subsequently in a counter clockwise direction. Afterinstalling the public address system the individualconnecting/disconnecting devices however can not know, which one oftheir contact points is the one located in the clock wise direction andwhich one is located in the counter clockwise direction. Therefore, inorder to determine the orientation of the connecting/disconnectingdevices these devices are brought into a default state, for example bypressing a dedicated switch button provided on the device, while nopilot signal is applied from the control and audio output module andwhile the power supply means does not supply power to the contactpoints. Subsequently the pilot signal is output or the control and audiooutput module will output switching pulses to initiate the closing ofthe switches, the connecting/disconnecting devices will sequentiallyclose there switches and will at that occasion determine the side whichclosing the switch first. In this manner the connecting/disconnectingdevices will determine their orientation in the loop. The configurationsetting means will set the contact point having the switch first closedas the first contact point and will set the other contact point as thesecond contact point.

In the preferred embodiment the system will be implemented with atwo-wire bus system, i.e. so that two wire loops are implemented and theloudspeakers are arranged between these loops. Each of theconnecting/disconnecting devices is configured to interrupt both loops.

According to the invention the public address system comprises aplurality of connecting/disconnecting devices as described above, anelectrical line comprising a plurality of portions connecting theplurality of connecting/disconnecting devices to each other, a pluralityof a loudspeakers connected in parallel on the line, and an control andaudio output module connected to the electrical line and configured tooutput an audio signal to the electrical line.

The control and audio output module is further configured to output apilot signal to the electrical line, wherein the pilot signal ispreferably in a range from 10 Hz to 25 kHz, more preferably in a rangefrom 10 Hz to 20 Hz, furthermore preferably in a range from 20 kHZ to 25kHZ, most preferably at 22 kHz, and the control means of the individualconnecting/disconnecting devices are configured to control the switchingmeans based on the pilot signal.

The pilot is preferably in a frequency range outside the audible rangeand can be used to provide the necessary power to charge a power sourceconnected with the power supply means, thus arriving at an efficient andreliable design.

According to the invention there is provided a method for detecting afailure in the electrical line of the public address system as describedabove. The method comprises a first step of switching the switchingmeans of the connecting/disconnecting devices described above from thesecond configuration into the first configuration upon detecting aninterruption of the pilot signal, a second step of applying by therespective power supply means electrical power to the respectiveportions of the electrical line via the respective first contact points,a third step of measuring at least one electrical characteristic at thefirst and/or the second contact points in order to determine the absenceof a short-circuit and/or a line breakage in the respective portion ofthe electrical line, and a fourth step of either switching from thefirst configuration into the second configuration, if the third stepdetects the absence of a short-circuit and/or a line breakage in therespective portion of the electrical line, or keeping the firstconfiguration if the third step detects a short-circuit and/or a linebreakage in the respective portion of the electrical line.

While in the above method reference is made to the first contact points,it goes without saying that instead of starting with the first contactpoints it is possible to start with the second contact points, as longas all connecting/disconnecting devices provided along the loopsimultaneously behave equal.

In case of using a two wired loop there will be a total of four contactpoints, two in each loop. That is, there will be two first contactpoints and two second contact points. The above method will then becarried out twice, once for each loop.

According to a preferred embodiment the method further comprising afifth step of switching the switching means in a third configurationwhere the second contact point and the power supply means areelectrically connected with each other, while the first and the secondcontact point are electrically disconnected from each other, and whilethe first contact point and the power supply means are electricallydisconnected from each other, a sixth step of applying by the respectivepower supply means electrical power to the respective portions of theelectrical line via the respective contact points, and a seventh step ofmeasuring at least one electrical characteristic at the first and/or thesecond contact point in order to determine the absence of ashort-circuit and/or a line breakage in the respective line portions;wherein the fifth to seventh steps are carried out between the third andthe fourth step.

With this implementation each connecting/disconnecting device willdetermine the presence/absence of a fault in the portion of theelectrical line connected to the first contact point and thepresence/absence of a fault in the portion of the electrical lineconnected to the second contact point. Thus it is possible to surelylocate and isolate the fault and to re-establish the operation of thepublic address system.

It is further preferred that the switching means comprises a firstswitch corresponding to the first contact point and a second switchcorresponding to the second contact point and a loudspeaker terminal forconnecting the loudspeaker provided between the first switch and thesecond switch, wherein the first switch is switched based on theelectrical characteristic at the first point, and the second switch isswitched based on the electrical characteristic at the second point.

With this configuration it is possible to isolate the fault in the lineportion while maintaining all loudspeakers operative.

As discussed above, each of the power supply means of theconnecting/disconnecting devices preferably applies at least one DCpulse, preferably a DC pulse pattern, to the line, and each of thecontrol means carries out in the third step and/or seventh step severalvoltage measurements corresponding to the DC pulse, preferably to the DCpulse pattern, in order to detect the absence of a short-circuit and/ora line breakage at the respective portion of the electrical line.

It is further preferred that results of each measurement are stored in astorage of the respective connecting/disconnecting device.

This allows to implement a historical database, which can be used wheninspecting the public address system, in order to identify creepingshorts or line breakings, i.e. a deterioration of the electrical lineover the time.

Upon detecting a short circuit in one loop of the two wired loopconfiguration the corresponding connecting/disconnecting device willkeep the switches directed towards the short circuit in a configurationisolating the respective portion of the lines for both loops.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following embodiments according to the invention will bedescribed with reference to:

FIG. 1 : showing a device for electrically connecting and disconnectingportions of an electrical line of a public address system according to afirst embodiment,

FIG. 2 : showing a device for electrically connecting and disconnectingportions of an electrical line of a public address system according to asecond embodiment,

FIG. 3 : showing a public address system according to the invention, and

FIG. 4 : showing a flow chart of the method according to the invention.

FIRST EMBODIMENT

By referring to FIG. 1 a device 1 for electrically connecting anddisconnecting portions of an electric line 7 of a public address systemaccording to a first embodiment will be described.

The device 1 comprises a control means 6, transforming and rectifyingmeans 81, charging means 83 connecting the transforming and rectifyingmeans 81 to a power source 82 to be charged, and a power supply means 8,to supply the power from the power source to a first contact point. Thepower source 81, which preferably is a capacitor, can be providedseparately from the connecting/disconnecting device 1.

The connecting/disconnecting device 1 further comprises a switchingmeans 4 which is provided between a first contact point A and a secondcontact point B. The switching means 4 can for example be an electricalcircuitry using transistor(s) and/or relay(s). The relay can for examplebe a mechanical relay using a spring and a coil. Preferably the relay isa bi-stable relay being able to stay in two different stable stateswithout being supplied with energy when the relay is in one of the twostable states and only needs to be supplied with electrical energy forswitching between the two stable states. In other words, the switchingmeans 4 has to be configured to electrically connect and disconnect thefirst and the second contact points A, B. More specifically theswitching means 4 has to be configured to switch between the firstconfiguration where the first contact point A and the power supply means8 are electrically connected with each other and the first and thesecond contact point A, B are electrically disconnected from each other,and a second configuration where the first contact point A and the powersupply means 8 are electrically disconnected and the first and thesecond contact points A, B are electrically connected with each other.

The connecting/disconnecting device 1 is shown only for one line. Incase of a two-wired loop an identical connecting/disconnecting device 1is provided for the other line of the loop as a combined device, capableof connecting/disconnecting both lines.

As can be seen in FIG. 1 , when the switching means 4 is in the firstconfiguration an electrical signal transmitted through the electricalline 7 being received at the first contact point A does not reach thesecond contact point B and therefore does not reach the respectiveportion of the electrical line 7 connected to the second contact pointB. In other words, the switching means 4 is configured to interrupt asignal and electrical energy transmission via the electrical line 7.

When the switching means 4 is in the first configuration the powersource 82 is electrically connected via the power supply means 8 and theswitching means 4 to the first contact point A. Therefore, electricalpower supplied from the power source 82 can be transmitted through theportion of the electrical line 7 connected to the first contact point A.The power source 82 connected to the supply means 8 shown in FIG. 1 is acapacitor. The capacitor is shown to be connected between the line andground. However, in case of a two-wired loop the capacitor will beconnected between the two lines.

Nevertheless, the invention is not limited to these specific example ofusing a capacitor as the power source 82 and also other power sourceslike for example a rechargeable battery, and/or an electricallyconnection to an external power supply line can be implemented.

As can be seen in FIG. 1 the power source 82, i.e. the electricalcapacitor, can be charged via the transforming and rectifying means 81and charging means 83 using the power supplied through the electricalline 7. The charging means 83 are electrically connected to transformingand rectifying means 81, which in turn is electrically connected to thefirst and the second contact point A, B and is configured to transformaltering current flowing in the electrical line 7 into direct current.Preferably the transforming and rectifying means 81 will selectivelymake use only of a small frequency spectrum of the electrical powertransmitted through the line, where this small spectrum is outside theaudible range.

As an alternative, the power source 82 can be charged via an external DCor AC power supply line and the transforming rectifying means 81 can beconnected to the external DC or AC power supply line. In a case wherethe power source 82 is charged via an external DC power supply line norectifying is necessary.

Referring back to FIG. 1 , beside being configured to transform thealtering current supplied via the line 7 into direct current, thetransforming and rectifying means 81 may further be configured to outputthe generated direct current within different voltage ranges and/ordifferent current ranges for driving the control means 6. Differentdevices such as single-phase-rectifiers, three-phase-rectifiers, and/orvoltage-multiplying-rectifiers known from the state of the art can beimplemented as the transforming and rectifying means 81. Additionally,it is not necessary to connect the transforming and rectifying means 81with both, the first and the second contact point A, B. It would also bepossible to connect the transforming and rectifying means 81 only withone of the two contact points, the first or the second contact point A,B.

Furthermore, the transforming and rectifying means 81 can comprise aDC-DC converter which is configured to convert a DC-current having ahigh voltage into a DC-current having a low voltage. That can benecessary, when a high voltage, for example 100 volt, is supplied viathe electrical line 7 and is intended to be used for charging the powersource 83. Nevertheless, such a DC-DC-current converter is optionallyand an implementation thereof depends on the voltage supplied via theline 7 and technical specifications of the power source 83 and/or thecharging means 82.

The device 1 for electrically connecting and disconnecting portions ofthe electrical line 7 of the public address system according to thefirst embodiment further comprises the above mentioned control means 6.The control means 6 is configured to control the switching means 4 basedon at least one electrical characteristic U1, U2, I1, I2 at the firstand/or the second contact point A, B. In other words, the control means6 is configured to measure at least one electrical characteristic U1, I1at the first contact point A, wherein the electrical characteristic canbe at least one of a current, a voltage, and an impedance. The sameapplies to the second contact point B. In the state of the art,different methods for measuring a current, a voltage and/or impedanceare known. It would for example be possible to measure a voltage and/ora current with an inductive measuring method, which is well known fromthe state of the art, and/or with a voltmeter and an ammeter,respectively.

In a preferred embodiment using a two-wired loop the voltage between thetwo wired is measured.

Preferably the electric characteristic is determined in a smallfrequency range. That is, the connecting/disconnecting device 1 isconfigured to be powered by a pilot signal in a small frequency range,outside the audible range, and the control means 6 will detect thepresence or absence of the pilot signal at least one of the contactpoints.

As described above, the control means 6 is configured to control theswitching means 4 such that the switching means 4 switches from thesecond configuration to the first configuration, when a voltage/pilotsignal level U1 at the first contact point A is lower than apredetermined threshold value Uset and/or a voltage/pilot signal levelU2 at the second contact point B is lower than the predeterminedthreshold value Uset. In other words, when a short-circuit occurs in arespective portion of the line 7 connected to one of the contact pointsA, B, the control means 6 is configured to detect a voltage drop/drop ofthe level of the pilot signal below the predetermined threshold valueUset by the above described measuring means and to control the switchingmeans 4, such that the electrical connection between the first contactpoint A and the second contact point B is interrupted.

More specifically, when a short-circuit occurs in the respective portionof the electrical line 7, which is connected to the first contact pointA, and/or a short-circuit occurs in the respective portion of theelectrical line 7, which is connected to the second contact point B, theswitching means 4 is switched from the second configuration to the firstconfiguration by the control means 6. In such a case, the first contactpoint A is now electrically connected to the power source 82 via thepower supply means 8. The power source 82 is configured to apply aDC-signal to the line 7 via the switching means 4 and the first contactpoint A. When the DC-signal is applied to the respective portion of theline 7 connected to the first contact point A the control means 6measures the electrical characteristic, i.e. the charging state of theportion of the electrical line between the first contact point A and thesecond contact point B of a neighbouring connecting/disconnecting devicealong the electrical line 7. If the portion of the electrical line isintact, the charging of the line—respectively the high level of thevoltage supplied from the power supply means—will result in a voltagedifferent from zero, which can be detected by the measuring means.

In a public address system a plurality of connecting/disconnectingdevices 1 of the first embodiment are connected via portions of theelectrical line 7. A plurality of loudspeakers is connected in parallel,i.e. in a two-wired line between the wires of the tow loops, i.e. “onthe line”. A control and audio output module is configured to output anaudio signal to the plurality of loudspeakers.

In such a public address system all connecting/disconnecting devices 1will be in the second configuration during normal operation. When ashort-circuit and/or a line breakage is detected—e.g. by an interruptionof a pilot signal—all the connecting/disconnecting devices 1 willsimultaneously switch into the first configuration, i.e. they willinterrupt the electrical connection between their respective first andcontact points A and B and they will connect the power supply means withtheir first respective contact point A.

When a short-circuit and/or a line breakage is present in a portion ofthe electrical line 7, the voltage at the contact point A will remainclose to zero, even if the relatively high output voltage level of thepower supply means is connected. Therefore, the device 1 forelectrically connecting and disconnecting portions of the electric line7 of the public address system according to the first embodiment of theinvention is able to determine, whether a short-circuit has occurred inthe respective portion of the electrical line 7 connected to the firstcontact point A.

Since the connecting/disconnecting device 1 is used as part of thepublic address system and is connected in series with a plurality ofsimilar connecting/disconnecting devices 1 along the electrical line 7,the connecting/disconnecting device 1 will receive at their secondcontact point B the DC-signal supplied by the power supply means of aneighbouring connecting/disconnecting device 1, provided that there isno fault in the respective portion of the electrical line 7 connected tothe second contact point B. Of course, all connecting/disconnectingdevices 1 have to be arranged so as to have the same orientation.

If the voltage level at the second contact point B raises, theconnecting/disconnecting device 1 will decide, that the portion of theelectrical line 7 connected with the second contact point B is free offault. On the other hand, if the level of the voltage remains low, theconnecting/disconnecting device 1 will decide, that the portion of theelectrical line 7 connected with the second contact point B isinterrupted or has a short-circuit. Thus the connecting/disconnectingdevice 1 of the first embodiment is able to detect the presence/absenceof a short-circuit and/or a line breakage on both portions of theelectrical line 7, to which the first and second contact points A, B areconnected, respectively.

When it is detected that no fault is present at all, theconnecting/disconnecting devices 1 will almost simultaneously switchfrom the first configuration back into the second configuration and thuswill close the loop. If on the other hand there is a fault within theelectrical line 7, the two connecting/disconnecting devices 1immediately adjacent to the fault will remain in the firstconfiguration, while all other connecting/disconnecting devices 1 willalmost simultaneously switch into the second configuration. The publicaddress system will then operate as two spur or branch lines.

The two connecting/disconnecting devices 1 immediately adjacent to theshort-circuit preferably will interrupt the supply of power through thepower supply means 8 to the contact point A after a predetermined time,in order to avoid a complete discharge of the power source 81.

Since the determining of the presence/absence of the fault, i.e. theshort-circuit or the line breakage, is done simultaneously for allportions of the electrical line 7, the time needed for this determiningis greatly reduced compared to the state of the art, where therespective portions of the electrical line are judged sequentially.Additionally, since the two connecting/disconnecting devices 1 locatedimmediately adjacent to the fault will remain in the firstconfiguration, the entire process of re-establishing the operation ofthe public address system can be accelerated compared to the repeatedsequential connecting operations of the state of the art describedabove.

In the first embodiment, the control and audio output module isconfigured to output a pilot signal via the electrical line 7. Thecontrol and audio output module is configured to output a constant pilottone as the above mentioned pilot signal to the electrical line 7,wherein the pilot tone is preferably outside the audible range andbetween 10 Hz to 25 kHz, more preferably in a range from 10 Hz to 20 Hz,furthermore preferably in a range from 20 kHz to 25 kHz, most preferablyat 22 kHz, and the control means 6 is configured to control theswitching means 4 based on the pilot tone outputted by the control andaudio output module.

More specifically, the control means 6 of each connecting/disconnectingdevice 1 of the public address system is configured to measure bymeasuring means accommodated in the control means 6, if the pilot signaloutput by the control and audio output module is received at therespective contact point, the first contact point A and/or the secondcontact point B. In a case, where the control means 6 recognizes, thatthe pilot signal output by the control and audio output module is nolonger received at the first contact point A and/or the second contactpoint B of one of the connecting/disconnecting devices 1, the controlmeans 6 controls the switching means 4 such that the switching means 4switches into the first configuration, as described above.

In other words, when the pilot signal is no longer received by one ofthe connecting/disconnecting devices 1, it is assumed that a fault inthe electrical line 7 has occurred. Then, the switching means 4 of thisconnecting/disconnecting devices 1 switches from the secondconfiguration into the first configuration and therefore provides anelectrical connection between the first contact point A and the powersource 82 via the power supply means 8 while simultaneously electricallydisconnecting the first and the second contact points A, B from eachother.

Subsequently, the above process for re-establishing the operation of thepublic address system is started.

As mentioned above, it is necessary that all connecting/disconnectingdevices arranged along the line have the same orientation. This can beassured by mechanical connections allowing only the connection of theportions of the line in one way.

In a modified first embodiment the output voltage of the power supplymeans 8 is modulated in the form of a DC-signal comprising a singleDC-pulse or preferably a DC pulse pattern. Since the plurality ofdevices 1 of the public address system are connected along theelectrical line 7 a connecting/disconnecting device 1 next to the oneconnecting/disconnecting device 1, applying the DC-signal to therespective first contact point A, can measure at its second contactpoint B, whether the DC pulse/the DC pulse pattern outputted by the oneconnecting/disconnecting device 1 reaches the second contact point Bthereof.

The connecting/disconnecting device 1 is further provided with a secondswitching means (not shown) to disconnect the power supply means 8 fromthe first contact point A and to connect the power supply means 8 to thesecond contact point B, while keeping the electrical isolation betweenthe two contact points A, B. This second switching means is operatedafter a predetermined first delay time. The single DC-pulse orpreferably the DC pulse pattern is subsequently applied to the secondcontact point B and can be received at the first contact point A of theneighbouring connecting/disconnecting device 1, within a secondpredefined delay time.

When the control means 6 of a connecting/disconnecting device 1 hasmeasured at both contact points A, B the DC pulse/the DC pulse patternwithin the first and second delay times, respectively, the control means6 controls the switching means 4 such, that the connecting/disconnectingdevice 1 returns to the second configuration. Otherwise, theconnecting/disconnecting device 1 remains in the first configuration anddisconnects the first contact point A and the second contact point B,i.e. interrupts the electrical line 7, and therefore isolates the faultoccurred in a respective portion of the line 7.

In this modified embodiment the switching of the second switching meanshas to be performed simultaneously for all the connecting/disconnectingdevices 1 along the electrical line. This is achieved by means of aswitching time control using the predetermined first and second delaytimes, which is triggered by the switching of the first switching means4 from the second configuration into the first configuration.

Compared to the first embodiment the modified first embodiment has thedrawback that the re-establishment of the public address system will notbe complete until the lapse of first and second delay times. However,the detection of a well defined DC-pulse or pulse pattern is easy toimplement, especially when limited power can be provided by the powersource 82, so that it might be difficult to raise the voltage level of along portion of the electrical line to a detectable level.

Advantageously the first modified embodiment is equipped with aresetting means for setting the connecting/disconnecting device 1 into adefault mode, an orientation determining means for determining in thedefault mode at which contact point the pilot signal is detected first,and a configuration setting means for setting the contact pointreceiving the pilot signal first as first contact point A and the othercontact point as second contact point B.

That is, in the default mode all connecting/disconnecting devices 1 arein the first configuration and the power sources 81 do not apply powerto the respective contact portions, either since they are (turn of)turned off or since they might be discharged. Subsequently the pilotsignal and/or a switch closing pulse is applied form the control andaudio output module to one end of the electrical line 7. The firstconnecting/disconnecting device 1 along the electrical line 7 willreceive the pilot signal/switch closing pulse, charge its powersource—if needed—and bring than the switch means 4 into the secondconfiguration. As a consequence, the pilot signal/next switch closingpulse will reach the second connecting/disconnecting device 1 along theelectrical line 7, which will than charge its power source—if needed—andswitch the switching means 4 into the second configuration. This processwill continue until the loop is closed and the control and audio outputmodule receives its own pilot signal/switch closing pulse through theother end of the electrical line 7. During this operation eachconnecting/disconnecting device 1 will recognize whether the pilotsignal/switch closing pulse has been supplied via contact point A or B,and will accordingly define said contact point—having received the pilotsignal/switch closing pulse first—as the first contact point, so as toset the orientation. Preferably the connecting/disconnecting device hasa reset switch for resetting the device into the default mode. The resetswitch can be implemented as software.

Of course this orientation setting procedure can be implemented as wellwith the first embodiment as described above.

SECOND EMBODIMENT

By referring to FIG. 2 a device 2 for electrically connecting anddisconnecting portions of an electric line 7 of a public address systemaccording to a second embodiment will be described.

In order to avoid rewording only differences between the first and thesecond embodiment will be described.

In difference to the first embodiment the device 2 according to thesecond embodiment comprises a switching means 4 having two switches,i.e. a first switch 41 and a second switch 42 (see FIG. 2 ). Between thefirst switch 41 and the second switch 42 a terminal for connecting adevice 2, such as a loudspeaker, is provided. The first switch 41 isconfigured to electrically connect the first contact point A and thepower supply means 8, and the second switch 42 is configured toelectrically connect the second contact point B and the power supplymeans 8. The control means 6 is configured to independently andseparately control the first and the second switches 41, 42.

A public address system according to the invention comprises a pluralityof devices 2 according to the second embodiment for electricallyconnecting and disconnecting portions of an electric line 7.Furthermore, a control and audio output module is connected to the line7 and configured to output an audio signal and/or a pilot signal, whichis a pilot tone, to the line 7. The electrical line 7 with the pluralityof devices 2 forms a loop line starting and ending at the control andaudio output module.

It goes without saying that in a preferred embodiment two loops areprovided and the connecting/disconnecting device is providedsymmetrically for each loop, i.e. in this case theconnecting/disconnecting device will comprise four switches, twoswitches on each loop.

By start-up of the public address system each of the devices 2 will bein the default mode. The control and audio output module will start tosupply the pilot signal and/or a switch closing pulse and/or the audiosignal to one end of the line 7 of one loop. The first and the secondswitch 41, 42 are in an open state, i.e. in a first configuration wherethe first contact point A and the second contact point B areelectrically disconnected from each other, while the first contact pointA and the second contact point B are electrically connected to the powersupply means 8, respectively.

The power source 82 will begin to be charged by the power transmittedthrough the electrical line 7. Once the power level of the power source7 is enough for powering the operation of the connecting/disconnectingdevice 2, the control means 6 will decide whether the pilot signal isapplied at contact point A or contact point B or whether a switchclosing pulse is received at contact point A or contact point B.

The control means 6 stores a timing information concerning to which oneof the first and the second contact point A, B the pilot signal, theswitch closing pulse and/or the audio signal has been applied first. Ingeneral, the control means 6 stores a timing information concerning theat least one electrical characteristic U1, U2, I1, I2 at the first andthe second contact point A, B. The first contact point A, B is then thecontact point to which the at least one electrical characteristic, i.e.the pilot signal or the switch closing pulse, has been applied first. Inconclusion, the other contact point is then the second contact point B.

When the control means 6 detects/measures the at least one electricalcharacteristic U1, U2, I1, I2 at the first contact point A of the device2, the switching means 4 is controlled by the control means 6 to switchinto a second configuration where the first contact point A and thesecond contact point B are electrically disconnected from the powersupply means 8, and where the first and the second contact points A, Bare electrically connected with each other, i.e. the first and thesecond switch 41, 42 are closed.

In a normal operation mode, the electrical line 7 form together with theplurality of devices 2 a closed loop starting and ending at the controland audio output module, i.e. the loudspeaker loop is closed duringnormal operation. In other words, in the normal operation of the publicaddress system the switching means 4 is in the second configuration,where the first contact point A and the power supply means 8 areelectrically disconnected, the second contact point B and the powersupply means 8 are electrically disconnected, and the first and thesecond contact points A, B are electrically connected with each othervia the first and the second switch 41, 42.

In case of absence of the pilot signal outputted by the control andaudio output module, for example a constant 22 kHz tone, all the devices2 detect a short-circuit and/or a line breakage at the loudspeaker loop,respectively. The control means 6 switches the switching means 4 intothe first configuration by opening the first switch 41. In other words,according to a method for detecting a failure in the electrical line 7of the public address system the switching means 4 is switched from thesecond configuration into the first configuration in a first step when afailure in the line 7 occurs.

Then all devices 2 will send a DC pulse, preferably a DC-pulse pattern,via their first switch 41 to the respective portion of the line 7connected to the first contact point A.

More specifically, during the DC pulse/the DC pulse pattern each device2 carries out at least one but preferably several voltage measures todistinguish whether the respective portion of the line 7 is free fromshort-circuit and/or a line breakage. Additionally, in an modifiedembodiment the control and audio output module might monitor whether itreceives the DC-signal from the first connecting/disconnecting device 2of the loop.

In general, in a second step at least one electrical characteristic ismeasured at the first and/or the second contact point A, B by thecontrol means 6. A result of the measurements is stored in the device 2and the first switch 41 is closed again, so as to disconnect the powersupply means 8 and the first contact point A. More specifically, thefirst switch 41 is switched by the control means 6 to be in a state ofelectrically disconnecting the first contact point A and the powersource 82 via the power supply means 8.

Simultaneously with the closing of the first switches 41, all devices 2will open their second switch 42 and send the DC pulse, preferably theDC pulse pattern, to the respective portion of the line 7 connected tothe second contact point B. During the DC pulse/the DC pulse patterneach device 2 carries out several voltage measures to distinguishwhether the respective portion of the line 7 is short-circuit and/or aline breakage free. In a modified embodiment, the control and audiooutput module can monitor whether it receives the DC-pulse/DC pulsepattern from the last connecting/disconnecting device 2 of the loop.Again, a result of the measurements may be stored in the respectiveconnecting/disconnecting device 2.

If both portions, the respective portion of the line 7 connected to thefirst contact point A and the respective portion of the line 7 connectedto the second contact point B, are indicated to be short-circuit and/orline breakage free, the switching means 4 is switched to the secondconfiguration, i.e. both switches 41, 42 are closed.

All devices 2 that have been decided to be short-circuit free and/orline breakage free for the respective portion of the line 7 connected tothe first contact point A, will switch their first switch 41 in aconfiguration of connecting the loudspeaker terminal to the line 7 viathe first switch 41, otherwise the first switch is electricallyconnected to the power supply means 8 and electrically disconnects theloudspeaker terminal from said portion of the electrical line 7.

All devices 2 that have been decided to be short-circuit free and/orline breakage free for the respective portion of the electrical line 7connected to the second contact point B, will switch their second switch42 in a configuration of connecting the loudspeaker terminal to the line7 via the second switch 42, otherwise the second switch is electricallyconnected to the power supply means 8 and electrically disconnects theloudspeaker terminal from said portion of the electrical line 7.

Subsequently the control means 6 will interrupt the supply of powerthrough the power supply means 8 in those connecting/disconnectingdevices, where one of the switches 41, 42 remains in the open state.

The first device 2 directly connected to the control and audio outputmodule switches its first switch 41 in a configuration of connecting theloudspeaker terminal to the line 7 via the first switch 41 in any case.This device will additionally maintain the second switch so as todisconnect the line, in order to avoid that the pilot signal isforwarded to the next connecting/disconnecting device along the loop, inorder to give the other connecting/disconnecting devices enough time tocheck the respective line portions. The first connecting/disconnectingdevice usually is provided as an integral part of the control and audiooutput module. Accordingly, a corresponding operation mode as firstconnecting/disconnecting device can be easily implemented.

Alternatively, it is possible to configure some or allconnecting/disconnecting devices such that, for the case that after arecognition of a short circuit and opening of the switches, the pilotsignal is immediately received at one of the contact points A, B, thecorresponding connecting/disconnecting device will decide that it is afirst connecting/disconnecting device and will close the switch on theside towards the control and audio output module and will keep the otherswitch open until the lapse of a predetermined waiting time, e.g. 1 to 4seconds.

The last device 2 directly connected to the control and audio outputmodule will behave in the same manner and switches its second switch 42in a configuration of connecting the loudspeaker terminal to the line 7via the second switch 42 in any case, as long as it receives the pilotsignal. Again this last connecting/disconnecting device usually will beprovided as an integral part of the control and audio output module.

Because all devices 2 on the loop work simultaneously, a short-circuiton the loop is separated and the operation of the public address systemis re-established fast and reliable independent of the number of devices2 in the public address system.

Furthermore, it is possible to connect the power source 82 via the powersupply means 8 between the first and the second switch 41, 42 similar tothe loudspeaker.

In case of a failure at the loudspeaker itself, detected by the devices2 as described above, each device 2 opens both of its switches and isthen completely isolated.

All devices 2—except the first connecting/disconnecting device of theloop, close their first switch 41 and send a DC pulse, preferably a DCpulse pattern, to the respective portion of the line 7 connected to thefirst contact point A. During the DC pulse/DC pulse pattern severalvoltage measures take place to distinguish whether the respectiveportion of the line 7 is short-circuit and/or line breakage free. Theresult is stored in the device 2 and the first switch 41 is openedagain.

All devices 2, except the last connecting/disconnecting device, closetheir second switch 42 and send the DC pulse, preferably the DC pulsepattern, to the respective portion of the line 7 connected to the secondcontact point B. During the DC pulse/DC pulse pattern several voltagemeasures take place to distinguish whether the respective portion of theline 7 connected to the second contact point B is short-circuit and/orline breakage free.

If the investigated part of the loop is indicated short-circuit freeand/or line breakage free the second switch 42 remains closed, otherwisethe second switch 42 opens again.

Because all devices 2 on the loop work simultaneously, a short-circuiton the loop is separated and the operation of the public address systemis re-established fast independent of the number of device 2 on theloop.

Finally, the first and the last connecting/disconnecting device willclose their respective switch on the side towards the control and audiooutput module and so reestablish the operation of the loop.

In a modified second embodiment the first and second switches 41, 42 arereversed. That is, in FIG. 2 , if both switches 41 and 42 are open,connecting their respective contact point and the power supply means,the power of the power supply means is applied to both portion of theelectrical line. Therefore, in order to avoid a complete discharge ofthe power source 81, the connecting/disconnecting device 2 has to beprovided with means for stopping the power supply after a certain time.

In the modified second embodiment, the switches 41 and 42 are reversed,so that the switches 41, 42 will connect the power supply means with theline connecting both switches 41, 42. Therefore, even if both switchesremain in this position, no significant discharge of the power source 81is to be expected.

FIG. 3 shows a configuration of a public address system. A control andaudio output module, although called digital output module DOM, isconnected with an electrical line 7 arranged so as to form a loop. Atmore or less regular intervals along the electrical line a plurality ofconnecting/disconnecting devices 2—also called line interrupt moduleLIM—are provided. Each LIM is associated with a loudspeaker. The LIMs ofthis system correspond to the modified second embodiment.

In the normal operation all LIMs are in the second configuration and thepilot signal is applied from the DOM to the electrical line 7 in e.g. aclockwise direction. If e.g. a short circuit, in general a fault,develops between the LIMs 2 a and 2 b the level of the pilot signal willdrop at all LIMs and all LIMs will switch into the first configuration.After testing the respective portions of the electrical line 7 to whicha LIM is connected, the LIM will return into the second configuration,provided that no short circuit is detected in one of said two portions.However, the LIM 2 a will detect a short circuit in the portionconnecting LIM 2 a and 2 b and will close only the first switch 41 andwill keep the second switch 42 open. The LIM 2 b on the other hand willas well detect the short-circuit and will close only the second switch42 and will keep the first switch 41 open. The DOM will recognize thatthe pilot signal does not reach the DOM at the other end of theelectrical line 7 and will conclude that there is a short-circuit.Consequently, the DOM will apply the pilot signal and the audio signalon both ends of the electrical line 7, and the system will operate as atwo branch lines.

FIG. 4 shows a flow chart for explaining the operation of theconnecting/disconnecting device of the invention.

At the beginning, i.e. after the installation of the public addresssystem all the LIMs are in the default mode or will be set into thedefault mode.

Then the orientation setting process is carried out, as described forthe first modified embodiment or for the second embodiment. At the endof this process all LIMs will know their orientation and will be setinto the second configuration. The loop will be closed and the normaloperation can start.

If necessary an additional position determining step will be carriedout, so as to allow each LIM to identify its position along the loop,i.e. whether it is a first or last LIM.

All LIMs will continuously monitor the contact points A and B for thepilot signal during normal operation. If the level of the pilot signaldrops below a predetermined threshold value, the re-establishmentprocess of the invention will be carried out.

In a first step the switching means 4 of the connecting/disconnectingdevices 1 will switch from the second configuration into the firstconfiguration upon detecting an interruption of the pilot signal.

In a second step the respective power supply means 8 will apply a DCpulse or pulse pattern (electrical power) to the respective portions ofthe electrical line 7 via the respective first contact points A.

In a third step the reception of the DC pulse pattern at the othercontact point B is monitored, in order to determine the absence of ashort-circuit and/or a line breakage in the respective portion of theelectrical line 7.

In a fifth step the switching means 4 are switched into a thirdconfiguration where the second contact point B and the power supplymeans 8 are electrically connected with each other, while the first andthe second contact point A, B are electrically disconnected from eachother, and while the first contact point A and the power supply means 8are electrically disconnected from each other.

In a sixth step the respective power supply means 8 applies the DC-pulseor pulse pattern to the respective portions of the electrical line 7 viathe respective contact points B.

In a seventh step the reception of the DC pulse pattern at the othercontact point A is monitored, in order to determine the absence of ashort-circuit and/or a line breakage in the respective portion of theelectrical line 7.

In a final step (fourth step) either a switching from the firstconfiguration into the second configuration, if the third step detectsthe absence of a short-circuit and/or a line breakage in the respectiveportion of the electrical line 7, or a keeping the first configurationif the third step detects a short-circuit and/or a line breakage in therespective portion of the electrical line 7 are carried out.

Subsequently, the normal operation of the public address system isre-established, and the system will operate either as a loop, if noshort circuit or line breakage could be detected at all, or it willoperate as two stich or branch lines.

Although advantageous embodiments have been described, a person skilledin the art is aware that he can combine these embodiments in anappropriate manner. E.g. it is possible to use LIMs according to themodified first embodiment together with LIMs of the second embodimentalong the same electrical line.

Furthermore, in the second embodiment the DC-pulse or pulse patternoutput by the LIMs can be replaced by signal corresponding to the pilotsignal, e.g. a sinus wave of 22 kHz. This will allow to simplify theLIMs, since the LIMs will have to be configured only to monitor onefrequency. In this case the LIMs should be configured so as to keep thefirst configuration for the entire delay time, regardless of thepresence or absence of the pilot signal.

1. A device, comprising: a first contact point; a second contact point;a power supply; a power source; an orientation determining means; and aswitch configured to: electrically disconnect the first contact pointand the power supply; and electrically connect the first contact pointand the second contact point; wherein the orientation determining meansis configured to determine at which contact point a pilot signal isdetected first; and wherein the power source is configured to chargeusing power supplied by the pilot signal.
 2. The device of claim 1,further comprising a resetting means configured to set the device to adefault mode.
 3. The device of claim 2, wherein the orientationdetermining means is configured to determine at which contact point thepilot signal is detected first in the default mode.
 4. The device ofclaim 1, wherein the switch is configured to electrically disconnect thefirst contact point and the power supply while electricallydisconnecting the first contact point and the second contact point. 5.The device of claim 1, wherein the pilot signal is a constant pilottone.
 6. The device of claim 1, wherein the pilot signal is between 10Hz to 25 kHz.
 7. The device of claim 1, wherein the power source is acapacitor.
 8. A method, comprising: charging a power source using powersupplied by a pilot signal; receiving the pilot signal at a contactpoint; setting the contact point as a first contact point responsive toreceiving the pilot signal first at the contact point; and settinganother contact point as a second contact point responsive to receivingthe pilot signal first at the contact point.
 9. The method of claim 8,further comprising setting a connecting/disconnecting device to adefault mode.
 10. The method of claim 9, further comprising setting theconnecting/disconnecting device to the default mode in response tosetting the contact point as the first contact point and the othercontact point as the second contact point.
 11. The method of claim 9,further comprising setting the connecting/disconnecting device to thedefault mode in response to starting-up a public address system.
 12. Themethod of claim 11, further comprising turning off the power source inresponse to the connecting/disconnecting device being set to the defaultmode.
 13. The method of claim 8, further comprising transformingalternating current (AC) supplied via an electrical line into directcurrent (DC).
 14. The method of claim 13, further comprising chargingthe power source connected to a power supply with the DC.
 15. A device,comprising: a first contact point; a second contact point; a powersupply; a power source; an orientation determining means; and acontroller configured to control the switch based on a pilot signal;wherein, responsive to the controller controlling the switch, the switchis configured to: electrically disconnect the first contact point andthe power supply; and electrically connect the first contact point andthe second contact point; wherein the orientation determining means isconfigured to determine at which contact point the pilot signal isdetected first; and wherein the power source is configured to chargeusing power supplied by the pilot signal.
 16. The device of claim 15,further comprising a control and audio output module configured tooutput the pilot signal.
 17. The device of claim 16, further comprisingan electrical line, wherein the control and audio output module isconfigured to output the pilot signal via the electrical line.
 18. Thedevice of claim 15, wherein the controller is configured to measure anelectrical characteristic at the first contact point.
 19. The device ofclaim 15, wherein the controller is configured to control the switch inresponse to neither the first contact point nor the second contact pointreceiving the pilot signal.
 20. The device of claim 18, wherein a faultin an electrical line is assumed in response to neither the firstcontact point nor the second contact point receiving the pilot signal.